Tuesday, October 6, 2015

Will Hurricane Oho Impact the Pacific Northwest?

Tuesday, October 6, 2015
3:29 pm

A tower atop Campbell Hall, Western Oregon University collapsing under the 100+ mph winds of the Columbus Day Storm. Credit: Wes Luchau, Statesman Journal

The Pacific Northwest has never gotten hit by a hurricane and never will. Our waters are simply too cold to sustain a tropical system. For a hurricane to form and keep its strength, you generally need to have 80+ degree water extending from the surface to at least 150 feet. The summer water temperatures off our coast are in the mid-50s due to the upwelling of deep, cold, nutrient-rich, acidic water (good for salmon, bad for Willapa Bay oyster larvae). But we can get the extratropical remnants of these storms, and due to the deep, tropical moisture source they provide, they can turn into quite vicious midlatitude cyclones.

The strongest of these was the Columbus Day Storm, which devastated the entire Pacific Northwest on October 12, 1962. No extratropical storm we've seen here or anywhere else in the United States can compare to the winds witnessed on that day. Not Superstorm Sandy, not the "Storm of the Century" of 1993, and certainly not the "Perfect Storm" of 1991. The map of peak gusts from the storm below speaks for itself.

Credit: Wikipedia User Spiritchaser

The Columbus Day Storm started out as Typhoon Freda, which reached category-3 status and had a minimum pressure of 948 millibars. As it traveled north, it became more entrained in the prevailing midlatitude westerly flow, and as a result, it weakened into an extratropical cyclone just before the International Date Line. As you can see, it sped up tremendously while retaining its structure. Just off the Northern California coast, it explosively redeveloped after interacting with a very strong jet stream, and the Columbus Day Storm was born (or resurrected, depending on how you see it).

The track of Typhoon Freda. The points are at 6-hour intervals, and circles represent a tropical system, while triangles delineate an extratropical one. Credit: Supportstorm

Yeah, it's fair to say I'm pretty obsessed with the Columbus Day Storm. It just kills me that I wasn't there to experience it. Nonetheless, I can't help but get excited every time there is talk of an ex-hurricane or typhoon hitting us. 

As it turns out, there is a specific tropical cyclone a little bit east of Hawaii. And the name of that tropical cyclone is Hurricane Oho.

Credit: Central Pacific Hurricane Center

Fortunately, Hurricane Oho does not appear to be a serious threat to the Pacific Northwest. This evening's model runs are forecasting a landfall near Haida Gwaii as a strong and compact extratropical storm. However, this morning's model runs showed it coming ashore Vancouver Island as a weak blob of rain. The general trend with the models has been to push Oho further westward and make it stronger, so while I doubt we will feel any effects here besides a few showers from a trailing cold front, it will be interesting to watch how this system evolves. The latest UW WRF-GFS model shows it making landfall as a 963 mb cyclone Friday morning, which is not that much weaker than the Columbus Day Storm. 

Valid 11:00 am PDT, Fri 09 Oct 2015: UW WRF-GFS

I'm not gonna lie... I'm a little bummed that Oho has its sights set on Alaska, and I don't think that will change. Still, it will be fascinating to study Oho's evolution from a tropical to an extratropical system as it races north, especially near the 53rd anniversary of the Columbus Day Storm. Stay tuned... this will be a storm to watch!

Thanks for reading,

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